The crazy promise behind the new mushroom diet

The latest diet craze to be touted by celebrities such as Kelly Osbourne and Katy Perry promises to help you lose fat everywhere but your breasts, and it’s called (wait for it) The Mushroom Diet or M-Plan.

By replacing one meal a day with mushrooms for two weeks, the people behind the diet say you can kiss the stubborn fat at your waist, hips and thighs good bye. Which would be amazing if it were true. "There's no magic food that can achieve spot-reduction," says Michelle Davenport, PhD, RD, director of nutrition for the health food delivery app Hasty.

That's not to say the M-Plan doesn't have good intentions. Mushrooms, for one, are a healthy food that can fight the flu and are high in fiber and vitamin D. And regularly swapping out a meal for plant-based dishes, says Dr. Davenport, can help lower our caloric intake by mixing in fiber, protein, and healthy fats, which can trick our bodies into feeling fuller for longer. (Meatless Mondays, anyone?)

It's just when you follow the diet based on the ungrounded claims of spot-reduction and mushrooms are magic that's the problem, says Dr. Davenport.